PAOD is characterized by a disorder of the blood vessels and also of blood cells called platelets which circulate in the blood and are activated in the early stages of blood clotting. We can assess these abnormalities of vessel and platelet function by measuring the urine and by ultrasound imaging of one of your forearm blood vessels (a safe procedure which does not require any blood draws, injection of contrast abents or exposure to radiation). The purpose of this study is to examine the effect of various types of treatments on these measurements. These treatments include: aspirin, indomethacin, and celecoxib, a new pain killer.